Photovoltaic modules, herein after PV modules, generate the most energy when oriented directly towards the sun. As the sun moves across the sky throughout the day, PV modules must be reoriented to keep them on the sun, in order to optimally generate energy.
Solar trackers are used to rotate photovoltaic (PV) modules to keep them perpendicular to the direct rays of the sun. Keeping the PV modules, as part of an array, at this orientation increases and ideally optimizes the amount of energy that can be generated by the array, because energy generated by the array drops off with the cosine of the angle of incidence of solar rays on the surface of the array.
In conventional single-axis trackers, PV modules are suspended above the ground in one or more horizontal rows, connected to a beam known as a torque tube. The torque tube, generally oriented along a North-South axis, is attached to a drive mechanism affixed to a support structure and actuated to incrementally rotate the photovoltaic array in place over the course of the day to maintain a relatively constant angle with the sun as the sun progresses westwardly through the sky.
Fixing PV modules in place with the driving mechanism make the support structures and torque tubes associated with the PV modules substantially more susceptible to wind damage. As the wind pushes on each PV module, each PV module applies torsion to the torque tube, and the additive forces tend to twist the torque tube along its main axis because at least one portion of torque tube is prevented from rotating due to the drive mechanism. Further, depending on the angle of the PV modules with respect to the wind flow, some wind conditions can cause damage by inducing oscillations in the torque tube assembly via forces applied to the PV modules. Consequently, preventing twisting of the torque tube in varying wind conditions is desirable to avoid maintenance and repair of the array.
Limiting maintenance is important because the viability of the array is based on the projected rate of return derived from comparing the fixed value of the energy generated over the lifetime of the system versus the costs of manufacture, installation and maintenance. In a multi-megawatt project, cost reductions of pennies per watt can be the difference between a project being viable or too expensive. Therefore, tracker designers are always seeking innovations to lower installation, hardware, and maintenance costs.
Accordingly, there remains a need for photovoltaic tracker mechanisms that allow for reducing maintenance and that are more efficient and cost effective.